For example, a Vodafone or Telstra branded phone in Australia will display the relevant logo and may only support features provided by that network (e.g.

Besides the locking, phones may also have firmware installed on them which is specific to the network provider. Most mobile phones can be unlocked to work with any GSM network provider, but the phone may still display the original branding and may not support features of the new carrier.

Mobile subscriber identification number (MSIN i.e., only one SIM can be used with the phone)Īdditionally, some phones, especially Nokia phones, are locked by group IDs (GIDs), restricting them to a single Mobile virtual network operator (MVNO) of a certain operator.

Mobile network code (MNC e.g., AT&T Mobility, T-Mobile, Vodafone, Bell Mobility etc.).

Mobile country code (MCC e.g., will only work with SIM issued in one country).

Generally phones can be locked to accept only SIM cards with certain International Mobile Subscriber Identities (IMSIs) IMSIs may be restricted by:

This is in contrast to a phone (retrospectively called SIM-free or unlocked) that does not impose any SIM restrictions. Technical restriction built into mobile phones by phone manufacturers for use by service providers to restrict the use of these phones to specific countries and/or networksĪ SIM lock, simlock, network lock, carrier lock or ( master) subsidy lock is a technical restriction built into GSM and CDMA mobile phones by mobile phone manufacturers for use by service providers to restrict the use of these phones to specific countries and/or networks.

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